Additive composition for use in special steel making

ABSTRACT

An additive composition for use in steel making, which comprises 84.8-99.3% by weight of an oxide component; 0.5-1.6% by weight of a metal component; and 0.04-0.07% by weight of a rare-earth element component is used in such a way that its four aliquots are each added in a blast furnace. The amount of the composition to be added is dependent on the steel to be produced. It is used at an amount of 15-17% by weight for special carbonic steel, at 18-20% by weight for special tool and die steel and at 21-25% by weight for special high-speed tool steel.

TECHNICAL FIELD

The present invention relates to an additive composition for use insteel making. More particularly, the present invention relates to anadditive composition which shows excellent activity in deoxidation,desulphurization and dephosphorization and makes slag to be of highfluidity. Also, the present invention is concerned with a method formaking special steel superior in mechanical properties, by. use of theadditive composition.

BACKGROUND ART

When making steel, lime (CaO) or fluorite (CaF₂), amounting up to 10% byweight of the amount of the ore to be fed, is conventionally added inmetal blast furnaces to remove impurities such as phosphorous (P) andsulfur (S) and to make the fluidity of slag better. Also, in order togive the mechanical properties required for the use of special steel,metal additives are frequently used. Such additives, however, play anincomplete role in removing he impurities from iron melts.

In the case of using the metal additives for alloy, their specificgravities are different from that of iron, the base material, so that animbalance occurs upon formulation of metals. In addition, the metalcomponents of the additives are often oxidized, which makes it moredifficult to obtain desired steel products. After all, expensive, highpurity metal additives are rising as an alternative, but give rise to anincrease in the production cost.

The problems ascribed to the difference in specific gravity may beovercome by stirring the iron melts of metal blast furnaces at constantspeeds, but this is extremely difficult. With the aim of avoiding thedifference of specific gravity between iron components and alloyadditive components in an iron melt, attempts have been made to makealloys in space, which is in a gravity-free state (e.g., M42 steelaccording to ASTM rule). The resulting alloys, however, are extremelyexpensive.

Catalytic agents formulated with rare metals were developed to improvesuch situations. For instance, 0.003% (30 ppm) of bromine element wasadded to a molten metal to remove P and S therefrom and ultimately tomake CBM steel of high hardenability. Recent research for rare earthelement combinations of lanthanum (La) and yttrium (Y) has allowed themaking of special steel superior in wear resistance, impact resistanceand toughness as well as reduced the amounts of conventional metaladditives. This method, however, has such a disadvantage that the rareearth elements require the processes necessary for dressing andsmelting.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to overcome theabove problems encountered in prior arts and to provide an additivecomposition for use in steel making, which is superior in deoxidation,desulphurization and dephosphorization and improves the fluidity ofslag.

It is another object of the present invention to provide a method formaking special steel superior in mechanical properties, including impactresistance, wear resistance and thermal resistance.

In accordance with an aspect of the present invention, there is providedan additive an additive composition for use in steel making, comprising:84.8-99.3% by weight of an oxide component; 0.5-1.6% by weight of ametal component; and 0.04-0.07% by weight of a rare-earth elementcomponent.

In accordance with another aspect of the present invention, there isprovided a method for making special steel, comprising the steps of.adding over four times, four aliquots of the additive compositioncomprising 84.8-99.3% by weight of an oxide component; 0.5-1.6% byweight of a metal component; and 0.04-0.07% by weight of a rare-earthelement component at an amount of 15-25% by weight of a scrap iron baseto be molten, in a blast furnace while the temperature is maintained at1,600-1,700° C.; removing slag from an iron melt in the furnace; andcarburizing if the iron melt is short of carbon content.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1a and 1 b are microphotographs showing the structures of aconventional steel product and a special high-speed tool steel of thepresent invention, respectively.

BEST MODES FOR CARRYING OUT THE INVENTION

The additive composition useful in making special steel, according tothe present invention comprises rare-earth elements (RE), metal elementsand metal oxides.

Belonging to the group IIIa in the Periodic Table, the rare-earthelements are composed of 17 elements, that is, scandium (Sc) with anatomic number of 21, yttrium (Y) with an atomic number of 39, and therare-earth metals, which are divided into the light rare-earth metalsranging, in atomic number, from 57 to 64 and the heavy rare-earth metalsranging, in atomic number, from 65 to 71. In the present invention, allor combinations of the rare-earth elements inclusive essentially of Ce,Nd, Sm, Pr, Eu, Gd and Dy, may be used.

La with atomic number 57, which is believed to give thermal resistanceto the steel of the present invention, is preferably added at an amountof 0.009-0.01% by weight (90-100 ppm) based on the total weight of thescrap iron to be fed. Regarding the amounts of the other rare earthelements, 0.012-0.014% by weight (120-140 ppm) are preferable for Cewith 15 atomic number 58, 0.0004-0.0006% by weight (4-6 ppm) for Pr withatomic number 59, 0.0009-0.0011% by weight (9-11 ppm) for Nd with atomicnumber 60, 0.0009-0.0011% by weight (9-11 ppm) for Sm with atomic number62, 0.0001-0.0003% by weight (1-3 ppm) for Eu with atomic number 63,0.0009-0.0011% by weight (9-11 ppm) for Gd with atomic number 64,0.0005-0.0007% by weight (5-7 ppm) for Dy with atomic number 66,0.0001-0.0002% by weight (1-2 ppm) for each of Ho, Er and Tu with atomicnumbers 67, 68 and 69, respectively, 0.0002-0.0004% by weight (2-4 ppm)for Yb with atomic number 70, 0.002-0.004% by weight (20-40 ppm) for Scwith atomic number 21, and 0.004-0.005% by weight (40-50 ppm) for Y withatomic number 39. The total amount of all of the rare earth elements ispreferably on the order of 0.03-0.05% by weight (300-500 ppm) based onthe weight of the scrap iron to be fed.

Examples of the metals useful for the present invention include titanium(Ti) with atomic number 22, manganese (Mn) with atomic number 25,chromium (Cr) with atomic number 24, nickel (Ni) with atomic number 28,strontium (Sr) with atomic number 38, barium (Ba) with atomic number 56,and germanium (Ge) with atomic number 32. In accordance with the presentinvention, all or combinations of the metals, inclusive essentially ofTi, Mn and Cr, are used. In a preferable formulation of the composition,Ti is present at an amount of 1.1-1.5% by weight, Mn at 0.10-0.15% byweight, Cr at 0.01-0.05% by weight, Ni at 0.01-0.03% by weight, Sr at0.05-0.07% by weight and Ba at 0.04-0.06% by weight.

As for the metal oxides, they comprise SiO₂, Al₂O₃, CaO, MgO, Na₂O, K₂O,CoO₃ and Fe₂O₃. When being molten along with an iron base material in ablast furnace, CaO improves the fluidity of slag in cooperation with therare earth elements. SiO₂ contributes to the absorption of impuritieswhile MgO is preventive of mesotherm. Deoxidation of the iron melt iseffected by Al₂O₃.

In accordance with the present invention, the metal oxides are containedat an amount of 84.8-99.3% by weight, based on the total weight of thecomposition, in order to make use of the functions of the oxides.

In accordance with the present invention, the composition comprises8-10.4% by weight of CaO, 43-45.5% by weight of SiO₂, 8-10.4% by weightof MgO, 13-15.5% by weight of Al₂O₃, 3-4.8% by weight of Na₂O, 1.5-1.9%by weight of K₂O, 0.3-0.5% of CoO₃, and 8-10.3% by weight of Fe₂O₃,based on the total weight of the composition.

Preferably, the additive composition has a particle size of 10 mesh orless. In order not to lose calories while melting iron materials in ablast furnace, the temperature mist be maintained at at least 1,600° C.upon feeding the additive composition.

For making general steel, the additive composition is used at an amountof 0.01-0.10% by weight of the weight of the iron material to be fed.However, the amount of the additive composition depends on the kinds ofthe steel to be produced. The additive composition is added at an amountof 15-17% by weight of the iron material to be fed, for special carbonictool steel, at 18-20% by weight for special tool and die steel, and at21-25% by weight for special high-speed tool steel.

When scrap iron is melted in a blast furnace, metal carbides(M_(x)C_(y)) and iron carbide (Fe₃C) are formed by the actions of themetal components while the rare-earth elements exert potent deoxidation,desulphurization and dephosphorization in the iron melt. In addition,the oxides play a role in improving the fluidity of the iron melt. As aresult, the metal carbides and iron carbides together form tightcementite structures in which hexagonal systems are introduced,shortening intercarbonic distances. The carbon steel having such ahexagonal spheroidite is highly resistant to impact, wear and heat.Also, it is greatly improved in hardness and tension and easy toheat-treat without deformation. Consequently, the additive compositionof the present invention penetrates into steel by virtue of the affinityand catalytic activity of itself upon melting in a furnace, leading to agreat improvement in quality of steel.

A better understanding of the present invention may be obtained in lightof the following examples which are set forth to illustrate, but are notto be construed to limit the present invention.

EXAMPLE I Additive Composition for Use in Steel-Making

An additive composition was prepared as indicated in Table 1, below.

TABLE 1 Oxides Metals Rare-Earth Elements Component wt % Component wt %Component wt % Y 0.0043 La 0.0095 Ce 0.0131 SiO₂ 45.45 Ti 1.13 Nd0.00715 Al₂O₃ 15.33 Mn 0.13 Sm 0.0010 CaO 10.19 Cr 0.04 Pr 0.0005 MgO10.07 Ni 0.02 Eu 0.0002 Na₂O 4.55 Sr 0.06 Gd 0.00107 K₂O 1.79 Ba 0.05 Dy0.00062 CoO₃ 0.48 Ge Ho 0.00010 Fe₂O₃ 10.18 Er 0.00011 Tm 0.00013 Yb0.0005 Sc 0.0035 U 0.00007 Sum 98.05 1.43 0.04185

The total weight was 99.51185% while ignition loss was 0.48815%.

EXAMPLE II

In making special steel, the additive composition of Example I was usedat an amount of 0.08% by weight on the total weight of raw scrap iron(with a content of ca. 0.3% of C, ca. 0.15% of Si and ca. 0.1% of Mn).While four aliquots of the additive composition were each added to theblast furnace, the temperature was always maintained at 1,650° C. tocompletely dissolve the composition. At this time, a large ignition losswas highly apt to be produced. Thus, slag must be removed with cautionagainst the ignition loss. Thereafter, carburization was executed if thecarbon content was measured to be short.

Increasing the fluidity of the slag, the rare-earth elements served toremove phosphorous and sulfur from the molten metal. They wereassociated with sulphur to give particles such as RE₂O₂S and RE₂S₃ orsulfides such as RES which were, then, removed as slag. Some rare-earthelements were associated with Al₂O₃ to form REA1₁₁O₈ particles whichwere also removed as slag. That is, rare-earth elements also served as apotent deoxidizer of depriving dissolved oxygens of the metal molts.Therefore, this deoxidation effect could considerably reduce the amountof the deoxidizer added, such as ferro-silicon (Fe—Si) andferro-manganese (Fe—Mn).

Of the rare-earth elements, La, Y and Ce showed potent catalyticactions. They each combine with carbon at a ratio of one or twomolecules per one carbon to give metal carbides which can make thestructure of steel better than can iron-carbide (Fe₃C) called cementite.

Taken together, the functions of the rare-earth elements make itpossible to make high quality special steel which is remarkably free ofphosphorous and sulfur, both causing brittleness, and is greatlyimproved in mechanical properties. Consequently, the additivecomposition according to the present invention allows the making ofspecial steel superior in mechanical properties, at lower productioncosts than do conventional additive compositions.

The rare-earth elements added in an electric furnace fiercely react withthe iron melts boiling therein, so they are spontaneously mixedtogether. The iron melts are greatly improved in fluidity by virtue ofthe oxides of the additive composition, such as CaO. Meanwhile, theimpurities resulting from the dephosphorization, desulphurization anddeoxidation, such as RE₂O₂S, REA1₁₁O₁₈, RES and RE₂S₃, are absorbed inthe slag formed by SiO₂, CaO, MgO. The slag rises to t he surface of theiron melts to shield the iron melts from being in contact with the sir,thereby preventing the alloy elements from being oxidized. The variousmetals of ores are associated with carbon under the potent catalyticaction of La, Y and Ce to form metal carbides (M_(x)C_(y)) in thepresence of which the resulting alloy can have superior alloystructures. Cooperating with one another, the additives of the presentinvention make desired alloy. After taking off the slag and executing afinal deoxidizing process, the iron melts are introduced into ingotcases which have a size suitable for rolling and forging. The ingotsthus obtained are immediately subjected to annealing before quenching,to rolling or forging at 1,200° C., and to heat treatments depending ontheir uses.

EXAMPLE III Special Carbonic Tool Steel

Using the additive composition as indicated in Table 1, special carbontool steel was made in a similar manner as that of Example II.

That is, an additive composition comprising 0.04% by weight or more ofthe rare-earth elements, 98% by weight or more of the oxides and 1.4% byweight or more of the metal elements, was added at an amount of 15-17%by weight per ton of scrap iron, followed by addition of 1.5 kg offerro-titan (Fe—Ti) with a grade of 40%. Impurities were removed fromiron melt by the cooperation of the deoxidation due to the catalyticaction of the rare-earth elements with the deoxidation, desulphurizationand dephosphorization due to the reactions of the oxides, and 40% byweight of the ferro-titan (Fe—Ti) added was made to incorporate in theiron melt, to give five types of novel rare-earth special carbonic toolsteel called KRS-2300 series, as shown in Table 2, below.

TABLE 2 Rare-Earth Special Carbonic Tool Steel in KRS-2300 SeriesKRS-2300 series JIS ASTM C Si Mn P S KRS-2301 SK-1 W-13 1.30-1.50 0.350.50 <0.020 <0.020 KRS-2302 SK-2 W-11 1.10-1.30 0.35 0.50 <0.020 <0.020KRS-2303 SK-3 W1-9 0.90-1.10 0.35 0.50 <0.020 <0.020 KRS-2304 SK-4 W1-80.70-0.90 0.35 0.50 <0.020 <0.020 KRS-2305 SK-5 W1-7 0.60-0.70 0.35 0.50<0.020 <0.020

EXAMPLE IV Special Tool and Die Steel

Using the additive composition as indicated in Table 1, special tool anddie steel was made in a similar manner as that of Example II.

An additive composition comprising 0.04% by weight or more of therare-earth elements, 98% by weight or more of the oxides and 1.4% byweight or more of the metal elements, was added at an amount of 18-20%by weight per ton of scrap iron, followed by the iron melt by thecooperative action of the rare-earth elements, the oxides and theferro-titan. That is, the rare-earth elements catalyzed deoxidationwhile the oxides showed deoxidation, desulphurization anddephosphorization. In addition, when 40% of the added ferro-titan wasincorporated in the iron melt, its potent deoxidation and catalyticaction promoted to form iron carbide structures and titanium carbidestructures, which led the alloy to spherodized structures, together. Tentypes of novel rare-earth special tool and die steel called KRS-2200series as shown in Table 3, below, were made.

TABLE 3 Rare-earth Special Tool and Die Steel in KRS-2200 SERIES KRSSeries JIS ASTM C Si Mn P S Ni Cr Mo W V KRS- SKS51 L6 0.75- 0.35 0.50<0.02 <0.02 1.3- 0.20- — — — 2201 0.85 2.0  0.50 KRS- SKS21 — 1.00- 0.350.50 <0.02 <0.02 — 0.20- — 0.50- 0.10- 2202 1.10 0.50 1.00  0.25  KRS-SKS11 F2 1.20- 0.35 0.50 <0.02 <0.02 — 0.20- — 3.00- 0.10- 2203 1.301.00 4.00  0.30  KRS- SKS4 — 0.45- 0.35 0.50 <0.02 <0.02 — 0.20- — 0.50-— 2204 0.55 0.50 1.00  KRS- SKS44 W_(2-8 1/2) 0.80- 0.35 0.50 <0.02<0.02 — — — — 0.10- 2205 0.90 0.25  KRS- SKS95 W5 0.80- 0.35 0.50 <0.02<0.02 — 0.20- — — — 2206 0.90 0.60 KRS- SKS94 — 0.90- 0.35 0.8- <0.02<0.02 — 0.20- — — — 2207 1.00 1.1 0.60 KRS- SKS3 01 0.90- 0.35 0.9-<0.02 <0.02 — 0.20- — — — 2208 1.00 1.2 0.60 KRS- SKD11 D2 1.40- 0.400.60 <0.02 <0.02 — 11.0- 0.80- — 0.20- 2209 1.60 13.0 1.20  0.50  KRS-SKD12 A2 0.95- 0.40 0.6- <0.02 <0.02 — 4.50- 0.20- — 0.20- 2210 1.05 0.95.50 1.20  0.50 

The qualities of the steel obtained were examined and the results aregiven as shown in Table 4, below.

TABLE 4 Mechanical Properties of KRS-2200 Series Special Tool and DieSteel* Tensile Yield Strength Point Elongation Reduction ImpactQuenching Hardness Samples (kgf/mm²) (kgf/mm²) (%) Area (%) (kgf/mm²)Avg. High Mid. Low KRS- 90.5 45 15.5 28 12 63.5 64 63.5 63 2205 KRS-92.5 41 15 8.5 9 64.5 65 64.5 64 2206 *tested in Korea AdvancedInstitute of Science and Technology (KAIST), Korea

Hardness was measured to be homogeneous over many parts of the samples.They were higher in tensile strength and elongation than correspondingJIS′. In addition, they were also measured to be strong and veryresistant to wear and impact.

Heat treatments were made on the special tool and die steel in KRS-2200series, according to the present invention, and corresponding mechanicalproperties were analyzed and their results are given as shown in Table5, below.

TABLE 5 Heat Treatments and Mechanical Properties of KRS-2200 Series KRSseries JIS ASTM Annealing Quenching Tempering KRS-2201 SKS51 L6 900-925°C. HB207 80-1,025° C. 205-540° C. HRC > 62 Slow Cooling Oil. Water AirKRS-2202 SKS21 — 900-925° C. HB201 80-1,025° C. 205-540° C. HRC > 63Slow Cooling Oil. Water Air KRS-2203 SKS11 F2 900-925° C. HB21780-1,025° C. 205-540° C. HRC > 65 Slow Cooling Oil. Water Air KRS-2204SKS4 — 900-925° C. HB207 80-1,025° C. 205-540° C. HRC > 63 Slow CoolingOil. Water Air KRS-2205 SKS4 W_(2-8 1/2) 900-925° C. HB201 80-1,025° C.205-540° C. HRC > 66 Slow Cooling Oil. Water Air KRS-2206 SKS95 W5900-925° C. HB212 80-1,025° C. 205-540° C. HRC > 63 Slow Cooling Oil.Water Air KRS-2207 SKS94 — 900-925° C. HB217 80-1,025° C. 205-540° C.HRC > 64 Slow Cooling Oil. Water Air KRS-2208 SKS3 01 900-925° C. HB21780-1,025° C. 205-540° C. HRC > 64 Slow Cooling Oil. Water Air KRS-2209SKD11 D2 900-925° C. HB223 80-1,025° C. 205-540° C. HRC > 65 SlowCooling Oil. Water Air KRS-2210 SKD12 A2 900-925° C. HB217 80-1,025° C.205-540° C. HRC > 64 Slow Cooling Oil. Water Air

Comparison between the KRS-2200 series special tool and die steel andthe corresponding JIS′ was made with regard to mechanical properties andthe results are given as shown in Table 6, below.

TABLE 6 Comparison between KRS-2200 Series and JIS Heat Treatment/Properties KRS-2205 SKS44 (JIS) KRS-2208 SKS-3 (JIS) Heat TreatmentQuenching 980-1,025° C. 760-820° C. 980- 1,025° C. 830-880° C. Water OilOil. Water Oil Tempering 205-540° C.   150-200° C. 205-540° C.  150-200° C. Air Air Air Air HRC >66 >62 >66 >62 Annealing 925-980° C.  730-760° C. 920-980° C.   750-200° C. Slow Slow Slow Slow HB <203 <213<207 <217 Properties Impact <10 >6.5 >8.3 >5.5 Tensile Strength(kg/m) >90 >50 >90 >55 Elongation (%) >18 >8.5 >16 >7.5

As apparent from Table 6, the KRS-2200 series of the present inventionare superior to corresponding JISs in various mechanical properties,including hardenability, hardness, tensile strength, impact resistance,wear resistance and processability. Upon heat treatment, the specialtool and die steel of the present invention showed almost nodecarburization or deformation.

EXAMPLE V High-Speed Tool Steel

Using the additive composition as indicated in Table 1, high-speed toolsteel was made in a similar manner as that of Example II.

An additive composition comprising 0.04% by weight or more of therare-earth elements, 98% by weight or more of the oxides and 1.4% byweight or more of the metal elements, was added at an amount of 21-25%by weight per ton of scrap iron, followed by addition of 3 kg offerro-titan (Fe—Ti) with a grade of 40%. Impurities were removed fromthe iron melt by the cooperative action of the rare-earth elements, theoxides and the ferro-titan. That is, the rare-earth elements catalyzeddeoxidation while the oxides showed deoxidation, desulphurization anddephosphorization. In addition, when 40% of the added ferro-titan wasincorporated in the iron melt, its potent deoxidation and catalyticaction promoted to form iron carbide structures and titanium carbidestructures, which together led the alloy to spherodized structures. Tentypes of novel rare-earth high-speed tool steel called KRS-21 00 seriesas shown in Table 7, below, were made.

TABLE 7 Rare-Earth High-Speed Tool Steel in KRS-2100 Series KRS seriesJIS ASTM C Si Mn P S Cr Mo W V Co KRS- SKH2 T 1 0.73- <0.40 <0.40 <0.02<0.02 3.80- — 17.0- 0.80- — 2101 0.85 4.50 19.0 1.20 KRS- SKH3 T 4 0.73-<0.40 <0.40 <0.02 <0.02 3.80- — 17.0- 0.80- 4.50- 2102 0.80 4.50 19.01.20 5.50 KRS- SKH4 T 5 0.73- <0.40 <0.40 <0.02 <0.02 3.80- — 17.0-1.00- 10.0- 2103 0.80 4.50 19.0 1.50 11.0 KRS- SKH10 T 10 1.45- <0.40<0.40 <0.02 <0.02 3.80- — 11.5- 4.20- 4.20- 2104 1.60 4.50 13.5 5.205.20 KRS- SKH51 M 2 0.80- <0.40 <0.40 <0.02 <0.02 3.80- 4.50- 5.50-1.60- — 2105 0.90 4.50 5.50 6.70 2.20 KRS- SKH52 M 3 1.00- <0.40 <0.40<0.02 <0.02 3.80- 4.50- 5.50- 2.30- — 2106 1.10 4.50 5.50 6.70 2.80 KRS-SKH54 M 4 1.25- <0.40 <0.40 <0.02 <0.02 3.80- 4.50- 5.50- 3.90- — 21071.40 4.50 5.50 6.50 4.50 KRS- SKH56 M 36 0.85- <0.40 <0.40 <0.02 <0.023.80- 4.60- 5.70- 1.70- 5.50- 2108 0.95 4.50 5.30 6.70 2.20 7.00 KRS-SKH58 M 7 0.95- <0.40 <0.50 <0.02 <0.02 3.80- 8.20- 1.50- 1.70- — 21091.05 4.50 9.20 2.10 2.20 KRS- SKH59 M 42 1.00- <0.40 <0.50 <0.02 <0.023.80- 9.00- 1.20- 0.90- 7.50- 2110 1.15 4.50 10.0 1.50 1.40 8.50

The qualities of the steel obtained were examined and the results aregiven as shown in Table 8, below.

TABLE 8 Mechanical Properties of KRS-2100 Series Special High-SpeedTool* Wear Hot Quenching Hardncss (HRC) Sample Resistance HarnessToughness Grindability Avg. High Mid. Low KRS-2110 5. 3. 8. 5. 67.5 67.67.5 68. *tested in KAIST, Korea

Hardness was measured to be high and homogeneous over many parts of thesample. It was superior to corresponding JIS′ in grindability andtoughness. It was also measured to be high in wear resistance and impactresistance, low in impurity content and homogeneous in quality.

With reference to FIGS. 1a and 1 b, there are microphotographs showingthe structure of a conventional product and that of the specialhigh-speed tool steel of the present invention. As shown, the structureof the tool steel according to the present invention is tighter by 200%or more than that of the conventional product.

INDUSTRIAL APPLICABILITY

As described hereinbefore, the additive composition in accordance withthe present invention makes steel tight in structure and provides itwith a great improvement in the resistance to impact, wear and heat. So,the present invention is very useful to regenerate scrap iron.

The present invention has been described in an illustrative manner, andit is to be understood the terminology used is intended to be in thenature of description rather than of limitation. Many modification andvariations of the present invention are possible in light of the aboveteachings. Therefore, it is to be understood that within the scope ofthe appended claims, the invention may be practiced otherwise than asspecifically described.

What is claimed is:
 1. An additive composition for use in steel making,comprising: 84.8-99.3% by weight of an oxide component selected fromCaO, SiO₂, MgO, Al₂O₃, Na₂O, K₂O, CoO₃, Fe₂O₃, and any combinationthereof; 0.5-1.6% by weight of a metal component selected from Ti, Mn,Cr, Ni, Sr, Ba, Ge, and any combination thereof; and 0.04-0.07% byweight of a rare-earth element component selected from Y, La, Ce, Nd,Sm, Pr, Eu, Gd, Dy, Ho, Er, Tm, Yb, Sc, U, and any combination thereof.2. The additive composition as set forth in claim 1, wherein said oxidecomponent comprises 8-10.4% by weight of CaO, 43-45.5% by weight ofSiO₂, 8-10.4% by weight of MgO, 13-15.5% by weight of Al₂O₃, 3-4.8% byweight of Na₂O, 1.5-1.9% by 0.3-0.5% by weight of CoO₃, and 8-10.3% byweight of Fe₂O₃, based on the total weight of the composition.
 3. Theadditive composition as set forth in claim 1, wherein said metalcomponent comprises Ti, Mn and Cr.
 4. The additive composition as setforth in claim 3, wherein said metal component comprises 0.45-1.3% byweight of Ti, 0.1-0.2% by weight of Mn and 0.01-0.05% by weight of Cr,based on the total weight of the additive composition.
 5. The additivecomposition as set forth in claim 1, wherein said rare-earth elementcomponent comprises Ce, Nd, Sm, Pr, Eu, Gd and Dy.
 6. The additivecomposition as set forth in claim 5, wherein said rare-earth elementcomponent comprises 0.01-0.015% by weight of Ce, 0.005-0.01% by weightof Nd, 0.0005-0.0015% by weight of Sm, 0.0003-0.0006% by weight of Pr,0.0001-0.0003% by weight of Eu, 0.0005-0.0015% by weight of Gd and0.0005-0.0008% by weight of Dy.